Mood Disorders 
The syndrome of "seasonal affective disorder" (SAD) is a condition where depressions in fall and winter alternate with nondepressed periods in the spring and summer. It has been suggested that in order to be diagnosed as having SAD a patient must met the following criteria: a history of major affective disorder; at least two consecutive previous years in which the depressions developed during fall or winter and remitted by the following spring and summer; absence of any other Axis I psychiatric disorders; and absence of any clear-cut seasonality changing psychosocial variables that would account for the seasonal variability in mood and behavior. An opposite pattern, depressions in the summer and non-depressed periods in the winter ("summer SAD"), has also been described. These two types of SAD probably represent a subset of a variety of seasonal behavioral disorders. SAD has been included in the Revised Third Edition and in the Fourth Edition of the "Diagnostic and Statistical Manual of Mental Disorders " of the American Psychiatric Association as "seasonal pattern", an adjectival modifier of any form of seasonally recurrent mood disorders.